In continuous casting systems for copper and other metals, the molten metal from the metal furnace is transferred to a holding furnace from which the metal flows into a tundish. Generally, the molten metal is withdrawn continuously from the tundish at a predetermined rate by a siphon which supplies the molten metal to the casting wheel.
One problem with continuous casting systems for copper as well as other metals is proper control of the oxygen content of the molten metal as it is siphoned away from the tundish. In copper, a certain amount of oxygen is necessary in order to render certain impurities less harmful and the amount of oxygen desired is fairly critical.
Until now, the oxygen content in copper was generally controlled by one of two methods. Firstly, it is possible to control the oxygen content in copper by controlling the oxidizing-reducing character of the hot gases generated by the melting furnace burners. This method has, however, proved to be a difficult method to practice because a very small change in the oxidizing-reducing character of the burner gases results in a substantial change in the oxygen content of the copper. In the second method, the melting furnace is operated so that the resulting molten copper is too low in oxygen content, and the proper amount of oxygen is added to the molten copper in the tundish. While the second method is generally satisfactory, a problem has arisen in determining the precise amount of oxygen to be added to the molten copper in the tundish. In the past the oxygen dissolved in the molten copper in the tundish was measured manually, by conventional methods whenever the operator deemed it necessary, and then the proper amount of air was added to bring the oxygen content to the desired level.
With the advent of the oxygen probe (a type of galvanic cell providing an EMF output which is proportional to the amount of oxygen dissolved in the copper) the process of measuring the oxygen content in molten copper was substantially simplified and shortened because the oxygen probe provides a substantially immediate indication of the measured oxygen content. However, the problem of how much oxygen to add to the copper remains.